The present invention relates to a coupling member of a power transmission apparatus for a vehicle, in particular to the structure of a coupling member for a drive shaft.
Japanese Patent Provisional Application 2001-65538 discloses a coupling member of a power transmission apparatus, applied to a drive shaft for a vehicle.
This power transmission apparatus comprises a fiber reinforced plastic cylindrical drive shaft, and universal joints which are press fitted into the ends of the drive shaft. Fitting portions of the universal joints, which enter the drive shaft, have respective serration portions formed in the axial direction on the outer surface for serration fitting with the drive shaft.
A high-precision device or jig is required in order to align the respective axial centers of a universal joint and the drive shaft into a single axis when press fitting, therefore a tapered guide surface is generally formed at the tip of the fitting portion to ensure it is properly guided during fitting as well as to ensure mutual axial alignment.